704 COLOR-VISION AND COLOR-BLINDNESS. 



of ueutial tint, more or less dark, ia front of either. Tlie most incred- 

 ulous employer may be convinced by expedients of this kind that the 

 color-blind are not to be relied upon for the safe control of ships or of 

 locomotives. With regard to the whole question-lhereare many points 

 of great interest, both physical and physiological, which are still more 

 or less uncertain, but the practical elements have, I think, been well- 

 uigh exhausted, and the means of securing safety are fully in the hands 

 of those who choose to master and to employ them. The lanterns in 

 their various forms are useful for the purpose of thoroughly exposing 

 the color-blind and for bringing home the character of their incapacity 

 to unskilled spectators; but they are both cumbrous and superfluous 

 for the detection of the defect, which may be accomplished with far 

 greater ease and with equal certainty by the wool test alone. 



I have already mentioned that the examinations which have been 

 conducted in the United States, thanks to the indefatigable labors of 

 Dr. Joy Jeffries, have led to the discovery of an enormous and pre- 

 viously quite unsuspected amount of color ignorance, the condition 

 which is frequently mistaken for color-blindness by the methods of 

 examination which are in favor with railway companies and with the 

 board of trade; and this color ignorance has been justly regarded as a 

 blot on the American system of national education. It has therefore, 

 in some of the States, led to the adoption of systematic col or- teaching 

 in the schools; and for this purpose Dr. Joy Jeifries has introduced a 

 wall chart and colored cards. The children are taught, in the first 

 instance, to match the colors in the chart with those of the cards dis- 

 tributed to them, and when they are tolerably expert at matching they 

 are further taught the names of the colors. It must nevertheless 

 always be remembered that a knowledge of names does not necessarily 

 imply a knowledge of the things designated, and that color vision 

 stands in no definite relation to color nomenclature. Even this system 

 of teaching may leave a color-blind pupil undetected. 



